Method of forming swaged contacts using progressive die

ABSTRACT

The nose section of a printed circuit board connector stamped from a strip of metal has two different thicknesses achieved by progressively piercing a U-shaped hole in the strip to form a cantilevered lug oriented normal to the grain direction, and then swaging the lug to increase its width and reduce its thickness. The U-shaped hole provides clearance for the two dimensional growth of the lug resulting from the swaging operation without affecting the remainder of the strip which is then progressively pierced to form a cantilevered car oriented in a direction parallel to the grain with the swaged lug supported on the free end of the car. The cantilevered car is then progressively bent along the line perpendicular to the grain to turn the lug so that it defines a surface perpendicular to the car thus establishing the wiping finger of the contact.

O United States Patent [1113 5 4 [72] Inventors Herbert E. Ruehleman2,932,880 4/1960 Gellatly et al 1 13/1 19 Huntington Valley; 3,172,7183/1965 Lalonde 339/276 ieter Slobodzian, Philadelphia, Pa. 3,231,8481/1966 Ruehlemann 339/176 [211 App]. No. 770,461 3,327,372 6/1967 Berg113/119 [22] Filed Aug. 15, 1968 Prim ry Examiner-Richard J. HerbstDivision of Ser. No. 630,612, Apr. 13, 1967, Atmmey-D R Pressmanabandoned. [45] Patented Feb. 2, 1971 [73] Assignee Elco CorporationWillow Grove, Pa.

a corporation Delaware ABSTRACT: The nose section of a printed circuitboard connector stamped from a strip of metal has two different [54]METHOD OF FORMING SWAGED CONTACTS thicknesses achieved by progressivelypiercing a U-shaped hole 111 the strip to form a cantilevered lugoriented normal to Usmc PROGRESSIVE DIE the grain direction and thenswaging the lug to increase its sums "prawns Figs width and reduce itsthickness. The U-shaped hole provides [52] US. Cl.. 113/119, clearancefor h two dim n ional growth of the lug resulting 29/630 from theswaging operation without affecting the remainder of [51] Int. Cl 821d53/26 the Strip which is then progressively pierced to f a mi Fleld ofSearch evered car oriented in a direction parallel to the grain the29/63OC; 339/17. 176NP. 2 2. 2 swaged lug supported on the free end ofthe car. The cantilevered car is then progressively bent along the lineperpen- [56] References Cited dicular to the grain to turn the lug sothat it defines a surface UNlTED STATES PATENTS perpendicular to the carthus establishing the wiping finger of 2,600,190 6/ 1952 Batcheller 113/1 19 the contact.

aeawrHwefiwi-ifi i J u 1 I01 ii-k 65 at 1 -64 e4 50 2| 9 2| 2| p 7 12 1i I tained on printed circuit boards and includes an insulated casinghaving a groove to receive an edge of a printed circuit board to which aplurality of spaced conductive tracks lead from the circuitry on theprinted circuit board. Mounted in the casing are a plurality of spacedcontacts each of which has a nose section that resiliently engages therespective tracks for the purpose of establishing electrical engagementtherewith and providing a force on the printed circuit board resistingwithdrawal. Each contact also has a tail section to which conductors canbe attached for effecting internal and external connections with thecircuitry on the printed circuit board, and a body sectioninterconnecting the nose and tail sections.

Ideal contacts of the type described are distinguished by a differencein thickness and hardness between the nose section on the one hand, andthe body and tail sections on the other hand. The size and hardness ofthe tail section is dictated by the type of termination to be made, thecurrently popular one being the so-called solderless-wrapped connectionwhich has been standardized, in the main. to 0.025 inch and 0.045 inchsquare tails. Grade A phosphorous bronze provides the ideal degree ofhardness for connections of this type although this material is oftentoo soft to give the nose section the required yield stress.

When contacts of the type described are stamped from a strip of materialusing a progressive die, the thickness of strip is determined by thetail size of the contact, but such thickness is generally considerablygreater than the thickness that provides the proper deflectioncharacteristics for the nose section of the contact, For this reason, itis conventional to use twostage strip material fed into the die so thatthe nose section is stamped from the thinner portion of the stripadjacent one edge, and the tail section is stamped from the thickerportion adjacent the other edge. While this arrangement provides thedesired thickness differential between the nose and tail sections, thehardness differential frequently must be sacrificed at the expense ofthe tail section in order to obtain the requisite degree of hardness forthe nose section to accommodate the stresses induced therein bydeflection resulting from engagement with the printed circuit board.Accordingly, it is often necessary to use two-stage beryllium copperstrip rather than the less expensive phosphorus bronze in order toobtain a nose section that will not fail when deflected by the printedcircuit board, even though the tail section will be harder than optimum.

The use of two-stage beryllium copper strip results in contacts whichare considerably more expensive than contacts made from single-stagephosphorus bronze strip, and which LII lack the optimum tail softnessfor making solderless-wrapped terminations. Therefore, the primaryobject of the present invention is to provide a method for utilizingsingle-stage relatively inexpensive strip material to produce a contactwhose nose section is thinner and harder than the tail section. It is afurther object of the invention to produce from a single-stage strip, acontact with thickness variations within the nose section itself.

A nose section having a thickness and hardness differential incomparison to the tail section is achieved from metal strip using aprogressive die by progressively piercing a U-shaped hole in the stripalong one edge thereof to form a cantilevered lug, and then swaging thelug to reduce its thickness from a point short of the support for thelug to the free end thereof. The pierced hole in the strip providesclearance for the increase in width of the lug which can occur withoutlengthwise distortion of the strip. Such distortion, if it were tooccur, would buckle the strip or interfere with the alignment of thestrip at the various stations of the progressive die. After the swagedlug is trimmed and formed. the strip is blanked to produce a contactwhich has a work-hardened nose section thinner than the tail.

The more important features of this invention have thus been outlinedrather broadly in order that the detailed description thereof thatfollows may be better understood. and in order that the contribution tothe art may be better appreciated. There are, of course. additionalfeatures of the invention that will be described hereinafter and whichwill also form the subject of the claims appended hereto. Those skilledin the art will appreciate that the conception upon which thisdisclosure is based may readily be utilized as a basis for designingother structures for carrying out the several purposes of thisinvention. It is important, therefore, that the claims to be grantedherein shall be of sufficient breadth to prevent the appropriation ofthis invention by those skilled in the art.

The invention is described by way of example with reference to theaccompanying drawings, in which:

FIG. I is a sectional view of two card-edge connectors mounting aspecial bus-contact made in accordance with the present invention;

FIG. 2 is a end sectional view taken along the lines 2-2 of FIG. 1;

FIG. 3 is a top view of the connectors shown in FIG. 1 with only aportion of each casing shown;

FIG. 4 is a strip formed in a progressive die in accordance with thepresent invention and showing completed nose sections as well as all ofthe intermediate steps by which such sections are formed; and

FIGS. 5 to II are sectional views taken along lines 5-5 and lI-I 1,respectively, of FIG. 4.

Referring now to FIG. I, a special bus-strip contact produced from stripusing a progressive die in accordance with the present invention isdesignated by reference numeral 10. Strip 10 comprises elongated flatbar 11 constituting the body section of the contact and a plurality ofspaced support arms 12 integral with bar 11 an and projecting upwardlytherefrom and terminating in free ends 13 spaced from the bar. Strip 10is stamped from a strip of material such as grade A, phosphorus bronzewith the grain of the material running lengthwise as indicated by arrow14. Thus, support arms 12 are normal to the grain and lie in the sameplane as the bar. Depending downwardly from bar 11 are a plurality oftail sections 15 of square cross section with thickness and width equalto the thickness of bar 11. The tail sections 15, which are staggeredrelative to support arms 12 for a reason to be indicated, haveconsiderable length relative to their transverse dimensions and areideally suited for making solderless-wrapped terminations.

In addition to support arm 12, each nose section 16 includes a generallyflat connecting arm 17 of uniform thickness equal to that of support arm12, and a curved wiping finger 21 of lesser thickness. Arm 17 has afirst portion 18 spaced from and parallel to support arm 12 and a secondportion 19 angularly disposed at to the first portion 18 and extendingaway therefrom in a direction generally parallel to the grain direction14 of the metal bar. One end 25 of portion 18 of arm 17 is integral andcoplanar with the free end 13 of arm 12, and the other end 26 of portion19 of arm 17 lies adjacent to but spaced from bar 11. Tab 20, which isintegral with and of the same thickness as end 26 of arm 17, is bent outof the plane of the latter along a bend line 27 (FIG. 3) perpendicularto the grain of the metal. As will be explained below, the nose sectionof the contact in the region of bend 27 is not workhardened, and sincethe bend is oriented at a right angle to the grain, an approximately 90bend can be achieved with a radius of the same order of magnitude as thethickness of the tab and connecting arm, all without fracturing themetal.

Wiping finger 21 is integral with connecting arm 17 with transitionportion 22 of the wiping finger extending upwardly from the upper edge23( FIG. 2) of tab 20; the free end 24 of the wiping finger terminatesaway from bar 11 and has a curved surface 28 that is substantiallynormal to the plane of the support arm. Surface 28 is oriented so thatthe projection thereof substantially bisects bar 11 as shown in FIGS. 2and 3. The wiping finger has a thickness gradient that is normal to thegrain direction. and in particular. the thickness of the transitionportion 22 of the wiping finger decreases from the junction betweenupper edge 23 of tab 20 toward the free end 24 of the wiping fingervActually. over most of its length the wiping finger has a uniformthickness which is less than that of the connecting arm; thickness andthe length of the transition portion are parameters determining thespring rate of the nose section of the contact. In one form of theinvention, the thickness of bar 11 is 0.025 inch. the thickness ofsupport arm 12 is 0.017 inch. and the thickness of the uniform portionof wiping finger 21 is 0.0l inch. The wiping finger 21 may also bebifurcated by slot 29 for reasons concerned with vibrationcharacteristics of the wiping finger. A notch 22a (FIG. 2) may beprovided in the transition portion 22 of the wiping finger adjacent bend27 facilitates making the bend.

Contact is designed to furnish a supply voltage to a plurality ofprinted circuit boards plugged into a plurality of sidewise-alignedconnectors 30 mounted, for example. on a metal plate as shown in FIG. 1.Specifically, each connector includes an insulated casing 31 carrying aplurality of contacts individually engageable with the respectiveconductive pads on a printed circuit board (not shown) when the latteris plugged into the connector. Casing 31 includes an elongated base 32having two rows of spaced holes 33 at each location that is to receive acontact, each hole having essentially the same cross section as the tailsections of contact 10. For example, if the tail is 0.025 inch square.the holes may be 0.026 inch square to permit the tail to be insertedinto a hole from the upper side 34 of the base. Casing 31 also includesa pair of spaced vertical walls 35 on the upper side 34 of the baseadjacent the two rows of spaced holes. such walls terminating in a freeedge 36 that is notched at 37 in alignment with holes 33.

As seen in FIG. 1, holes 33 are arranged in lateral pairs in verticalslots 38 in opposite faces of walls 35. the slots being defined bylateral walls 39 provided with card-edge receiving slots 40 adapted toreceive an edge of a printed circuit board (not shown). Vertical walls35 are also provided with aligned transverse slots 41 that permit bar 11to pass completely through the casing 31 in a direction normal to thelength of the casing. When a plurality of connectors are mounted onmetal plate 42 in sidewise alignment. slots 41 in the connectors arealigned thus permitting bar 11 of the contact to pass from one connectorto another. In actual use. there are many such connectors and it shouldbe apparent that the number of connectors is not an important factor inthe present invention. Also. one or more contacts like that shown at 10can be used with the connectors, depending upon the circuitryrequirements of the printed circuit boards. Individual contacts (notshown) are provided at other locations in the connectors.

In fabricating the connector shown in FIG. 1, it is preferred topreassemble individual contacts in the insulated casings at eachlocation that does not require a bus-contact. Such individual contacts(not shown) have a nose section similar to that shown for contact 10,but the connecting arm does not extend across the width of slot 40.Moreover. the support arm is immediately above the body and tail sectionof the contact, and the tail section extends into a hole in base 32 ofthe casing adjacent the vertical wall containing the slot 38 withinwhich the wiping finger is contained, Since these contacts are entirelyconventional, there is no need to show their details. The tail sectionof these contacts has a pair of vertically spaced enlarged rounded ears43 that are larger than the hole size and serve to grip the plasticmaterial of the casing and so secure the contact to the casing. As seenin FIG. 1, base 32 of the easing is provided with a plurality of hubs 44aligned with the two rows of holes 33 in the base, such hubs beingpressed into aligned holes 45 in plate 42 to establish a friction fitthat retains the casing to the plate.

After the individual contacts are preassembled into the easings, thevarious casings are attached to metal plate 42 as indicated above. Atthis time. contact 10 can be inserted into the aligned casings byaligning the tail sections 15 with proper holes 33 in the base. In suchposition. support arms 12 will be contained within slots 41 in thecasings and portion 19 of each connecting arms 17 will bridge slotwithin which an edge of a printed circuit board is inserted. This is thereason arms 12 and sections 15 are staggered on bar 11.

As indicated previously. the free ends of tail sections 15 are insertedinto holes 33 in upper side 34 of the base of the easing. the 0.00l inchnominal clearance between the contact tails and the holes in the casingeffecting entry of the tails into the holes. A tool may be seatedagainst flattened free ends 13 of the support arms 12 for the purpose ofpushing the contact into the aligned casings until the free ends 24 ofthe contact are contained in notches 37 of the casings. In thisposition, the curved part 28 of each wiping finger 21 is spaced from awall 35 of a casing, and is laterally located in the recess 46 formedbetween the walls of the casing. Such curved part of the wiping fingerwill be engaged by a conductive pad on an edge of=a printed circuitboard (not shown) when the latter is inserted into slot 46 of a casing.

It is conventional to preload the wiping fingers to achieve the desiredperformance characteristics. This is achieved by providing laterallyextending preload tabs 47 on free end 24 of each wiping finger. eachsuch tab engaging a projecting ridge 48 in notch 37 on the insulatorcasing when the contact is fully seated for the purpose of initiallydeflecting the wiping finger from its no-load position. In such case,curved part 28 of the contact will lie closer to adjacent vertical wall35 than would be the case where tabs 47 and projections 48 not present.

Because contact 10 is a bus-strip contact, wherein the body section 11is common to each contact nose tail section, it lends itself to beingproduced in a progressive die from twostage material. Referring now toFIG. 4, a flat strip of metal is designated by reference numeral 50,such strip having a width slightly greater than the entire height of thecontact to be produced therefrom. and a thickness in a region 51adjacent upper edge 52 of the strip less than the thickness in a region53 adjacent the lower edge 54. Stop 55 in the top surface of strip isthe demarcation line between regions 51 and 53. Preferably, strip 50 isformed by milling region 51 from a coil of uniformly thick strip.

A progressive die is the term given to a metal forming machine in whicha plurality of metal-forming operations are carried out in apredetermined sequence on a continuous strip of metal intermittently fedinto the die. Such operations are achieved at spaced stations in the dierequiring an arrangement to intermittently index the strip through thedie in a precise manner. Pilot holes punched in the strip in a regionthat will not interfere with the finished product are usually used forindexing the strip properly.

Accordingly. when the strip is fed into the die, pilot holes 56 arepunched at a pilot punch station (not shown). The strip (containing onlypilot holes 56) is then indexed to the right (as seen in FIG. 4) untilits right end is located at the right edge of station A where a punchpierces closed holes 57, 58in region 51 adjacent edge 52, and closedhole 59 in region 53 adjacent edge 54. Hole 58 is rectangular andoriented in a direction perpendicular to the grain direction of thestrip and to demarcation step 55, at which one end of the hold holepreferably terminates. Hole 57, spaced from hole 58 also is elongated ina direction perpendicular to step 55 but terminates short thereof in anarrow reduced portion. Hole 59 establishes the free end or tip of tailsection 15.

After holes 57, 58 and 59 are punched, the strip is again indexed untilend 55' is located at the right edge of station B where the strip ispierced to interconnect holes 57 and 58 adjacent edge 52 and define aclosed U-shaped hole that forms a cantilevered lug directed toward edge52. At the same time additional holes 57, 58 and 59 are formed in theportion of the strip now located at station A. As seen in FIG. 5. lug 60is uniformly thick.

After indexing. end 55' is located at the right edge of station C wherethe cantilevered lug is swaged to reduce its thickness and increase itswidth as shown in FIG. 6. Simultaneously the portion of the striplocated at station B to is punched to form another cantilevered lug. andholes 57. S8 and 59 are punched in the portion of the strip located atstation A. The swaging of cantilevered lug 60 is at station C is donefrom a point short of step 55, leaving support portion 61 for the lug.Also the swaging is done to only a central strip of the lug to producelengthwise running ridges 62 as seen in FIG. 6. The thin section 63 ofthe swaged lug is now of a width slightly wider than the width of thewiping finger which is trimmed from the swaged lug at a succeedingstation. The lug will have a transition portion 22 which has a thicknessgradient normal to the grain direction 14. For most of the length of theswaged lug, however, the thickness is uniform and of a value less thanthat of region 51 with the result that the thickness of the lugdecreases from the junction between the lug and the support 61 thereforeto the uniform thickness according to a design that provides the desiredspring rate and stress distribution.

The rigidity of the blanked strip is maintained to permit it to be fedfurther into the die by vertical webs 64, which define holes 57 and 58in respective portions of the strip, and which are integral withhorizontal web 65 that interconnects webs 64 along edge 52 of the stripand bar 11. The width of holes 57 and 58 are such as to permit thewidthwise growth of lug 60 to occur during the swaging operation atstation C without distorting the remainder of the strip. So that theswaging does buckle or distort the strip or interfere with the pilotholes. In other words, growth of the lug due to swaging is confinedprecisely to the region of the strip associated with an individual nosesection and does not affect the overall length and width of the strip asit is fed into the die.

After lug 60 is swaged, the strip is indexed so that end 55' is at theright edge of station D where four lengthwise grooves 66 are coined intothe upper surface 67 of the swaged lug as shown in FIG. 7. These grooveswill later define the edges of the bifurcated surface 28 of thecompleted wiping finger, and are provided for the purpose of preventingthe edge of a printed circuit board from snagging on the wiping fingerduring an angular insertion of the printed circuit board into theconnector. It should be understood, of course, that simultaneously withthe coining operation at station D, the operations associated withstations A, B, and Gas well as the pilot station, also occur.

After these operations, the strip is indexed until end 55' is located atthe right edge of station E where the swaged and coined lug is slottedat 29 to form the bifurcated nose of the contact. As shown in FIG. 8,the die that slots the swaged and coined lug is precisely located sothat the inwardly facing edges of the slot are beveled. As before, theoperations already described at the previous stations occursimultaneously with the slotting, after which the strip is again indexeduntil end 55' is located at the right edge of station F. Here, theremainder of the wiping finger 21 is trimmed from the slotted lug asshown in FIG. 9, At this location, the wiping finger is still flat butis completely established except as to forming which occurs at stationG.

The trimmed lug is formed at station G, where the required concavecurvature is imparted to the wiping finger.

At station 11 support 61 is pierced or slotted to produce an L-shapedhole 68 that defines a cantilevered car 69 oriented parallel to graindirection 14. One leg of hole 68 is even with demarcation step 55 andthe other leg of the hole is parallel to web 64. Ear 69 is thussupported from vertical web 64 at a point remote from step 55 anddefines the development of connecting arm 17 and tab 20.

After this operation, the strip is indexed until end 55' is located atthe right edge of station I where the tab 20 is bent along line 27 untilsurface 67 of the blanked wiping finger faces to the left as seen inFIG. 4. Surface 67 (corresponding to surface 28 previously described) iscurved and is oriented at a right angle to web 64. At this station, thetop and bottom surfaces of the strip at the apex of the triangular formdefining hole 59 may be coined as at 71 to finish the free end of tailsec tion 15 after the latter is formed at a subsequent station.

After further indexing. the end 55 of the strip is located at the rightedge of station .I where closed hole is pierced to establish the tailsection 15 of the contact.

The vertical web 72 is removed at station K after indexing end 55 to theright edge of that location. In addition, web 64 is severed to establishsupport arm 12.

While the strip shown in FIG. 4 indicates grooves 66 are coined prior toblanking the wiping finger from a swaged lug, this is optional with thetool designer since the lengthwise edges of the wiping finger can becoined after such blanking. It should also be understood that the stepsillustrated in sections A through 11, where the nose section is swaged,pierced, and then formed, can be applied to forming individual contactsfrom single-stage strip using a progressive die. after which thecontacts can be blanked from the strip.

It should be noted that at station D less than the entire width of lug60 is swaged because the lug need be swaged to a width only slightlygreater than the width of the trimmed wiping finger. This featurereduces the swaging force requirement at station D. Still anotherobservation is in order with regard to the bending step that occurs atstation I. The bend occurs in a region of the car 69 that is notcold-worked, and is oriented so that'bending occurs along a line normalto the grain of the metal. Under these conditions a rather sharp bendcan be made without fracturing the metal.

Strip 50 shown in FIG. 4 actually has three thicknesses; the tail andbody section being of one thickness, namely 0.025 inch; and the nosesection having a differential thickness ranging from 0.017 inch for arms12 and 17 and tab 20 to 0.010 inch for the free end of the wipingfinger, Two-stage strip is actually used, but the principles involved inproviding a U- shaped hole to define a lug that can be swaged withoutdisturbing the indexing of the strip are applicable to individualcontact blanking as indicated previously.

We claim:

1. The method for progressively forming, from a strip of metal having agrain oriented in parallel to the longitudinal edges of said strip, thenose sections of contacts for a printed circuit board connector,comprising the following steps:

a. feeding said strip until a first portion thereof is at a firstpiercing station;

b. at said piercing section forming a U-shaped hole in said strip near alongitudinal edge thereof to form a first cantilevered lug which pointstowards said longitudinal edge and is perpendicular to said grainorientation;

c. feeding said strip until said first portion is at a swaging station;and

d. simultaneously l piercing a second portion of said strip at saidpiercing station to form a second cantilevered lug similar to said firstcantilevered lug, and (2) swaging said first cantilevered lug at saidswaging station to reduce its thickness and increase its width from thefree end thereof to a location spaced from the support region for saidfirst lug, said swaging producing a thickness gradient in said lug whichis perpendicular to said grain orientation, said U-shaped hole in saidstrip providing clearance for the increase in width of "the lug due toswaging, whereby said swaging will not produce lengthwise distortion ofsaid strip.

2. The method of claim 1, further including the step of feeding saidstrip until said first portion is at a second piercing station andsimultaneously (1) piercing a third portion of said strip at said firstpiercing station to fonn a third cantilevered lug similar to said firstcantilevered lug, (2) swaging said second cantilevered lug at saidswaging station to reduce its thickness and increase its width in amanner similar to the swaging of said first cantilevered lug, and (3)piercing said strip at said second piercing station in the region ofsupport for said first lug to produce a cantilevered ear which points ina direction parallel to said grain orientation so that said first lug.(3) piercing said strip at said second piercing station in the region ofsupport for said second lug to produce a cantilevered ear which supportssaid second lug in a manner similar to that by which said first lug issupported. and (4) at bending station. bending said cantilevered earsupporting said first lug along a line which is perpendicular to saidgrain orientation and which is located between the support region ofsaid cantilevered ear and said support region for said first lug.

1. The method for progressively forming, from a strip of metal having agrain oriented in parallel to the longitudinal edges of said strip, thenose sections of contacts for a printed circuit board connector,comprising the following steps: a. feeding said strip until a firstportion thereof is at a first piercing station; b. at said piercingsection forming a U-shaped hole in said strip near a longitudinal edgethereof to form a first cantilevered lug which points towards saidlongitudinal edge and is perpendicular to said grain orientation; c.feeding said strip until said first portion is at a swaging station; andd. simultaneously (1) piercing a second portion of said strip at saidpiercing station to form a second cantilevered lug similar to said firstcantilevered lug, and (2) swaging said first cantilevered lug at saidswaging station to reduce its thickness and increase its width from thefree end thereof to a location spaced from the support region for saidfirst lug, said swaging producing a thickness gradient in said lug whichis perpendicular to said grain orientation, said U-shaped hole in saidstrip providing clearance for the increase in width of the lug due toswaging, whereby said swaging will not produce lengthwise distortion ofsaid strip.
 2. The method of claim 1, further including the step offeeding said strip until said first portion is at a second piercingstation and simultaneously (1) piercing a third portion of said strip atsaid first piercing station to form a third cantilevered lug similar tosaid first cantilevered lug, (2) swaging said second cantilevered lug atsaid swaging station to reduce its thickness and increase its width in amanner similar to the swaging of said first cantilevered lug, and (3)piercing said strip at said second piercing station in the region ofsupport for said first lug to produce a cantilevered ear which points ina direction parallel to said grain orientation so that said first swagedlug will be supported on the free end of said cantilevered ear.
 3. Themethod of claim 2, further including the step of feeding said stripuntil said first portion thereof is at a bending station andsimultaneously (1) piercing said strip at said piercing station to forma fourth cantilevered lug similar to said first cantilevered lug, (2)swaging said third cantilevered lug at said swaging station to reduceits thickness and Increase its width in a manner similar to the swagingof said first cantilevered lug, (3) piercing said strip at said secondpiercing station in the region of support for said second lug to producea cantilevered ear which supports said second lug in a manner similar tothat by which said first lug is supported, and (4) at bending station,bending said cantilevered ear supporting said first lug along a linewhich is perpendicular to said grain orientation and which is locatedbetween the support region of said cantilevered ear and said supportregion for said first lug.